Numerically-controlled boring and milling machines are used in particular for forming variable profiles of revolution connected by curved sections.
Surfacing plates of the aforesaid type are already known, where the radial movement of the slide is controlled by a servo-coupling independent of the other axial movements of the machine. This technique necessitates a complex kinematic mechanism of the differential type, and use of an additional motor for the spindle or for the radial slide. In addition, this technique employs complex trains of pinions, or electrical connections difficult to construct and of uncertain reliability. The distribution of the rotary masses often is scarcely satisfactory and does not permit a high rotary speed to be achieved. In addition, the plays are difficult to take up.
It has also been proposed, for example in U.S. Pat. No. 2,404,433 to servo-couple the radial movement of the tool holder slide to the longitudinal movement of the boring spindle.
More precisely, this purpose is achieved by the construction of a surfacing plate comprising a hollow cylindrical body the rear end of which is fixed to the milling spindle of the machine tool and the front end of which carries the tool holder slide.
The servo-coupling mechanism comprises a central part coupled longitudinally on the side of the rear end of the cylindrical body, by a conical end piece to the boring spindle, slidable longitudinally inside the cylindrical hollow body and provided with a longitudinal rack connected kinematically by a set of pinions with a radial rack screwed onto the inner surface of the tool holder slide, situated in a plane perpendicular to the plane of the longitudinal racks of the central part and arranged so that the longitudinal movement of the boring spindle in the milling spindle is converted by the longitudinal racks of the central part, the set of pinions and the radial rack of the slide, into a radial movement of the slide.
Other more or less complex arrangements have been proposed. However, none enables the taking up of the play in the mechanical transmission by simple means, which is however necessary in order that the radial movement of the slide may follow the longitudinal movement of the boring spindle with precision.